Sincere as the performances are, they don't generate enough stage heat to forge a sustained connection either with each other or the audience.

Her cane crashes to the floor, her body crumples and a shockwave of sympathy grips the audience as Ellen Burstyn’s Amelia is brought face-to-face with the fatal consequences of her actions. It’s the climax of Ian Rickson’s revival of “The Children’s Hour.” But Burstyn is playing one of the villains, and the emotional center should belong to the teachers played by Keira Knightley and Elisabeth Moss. But sincere as their performances are, they don’t generate enough stage heat to forge a sustained connection with each other or the audience.

Thematically, the 1934 drama still fascinates. Predating the more resilient “The Crucible” by two decades, Hellman’s drama about teachers wrongly accused of lesbianism similarly exposes the corrosive power of lies and, specifically, rumor. In Rickson’s hands, it also addressees the distortions created by adolescent sexuality.

In an added prelude to Hellman’s script, Rickson presents a tomboyish Mary (Bryony Hannah) alone on a couch, consumed by an illicit novel and beginning to explore her body. Although the scene is convincing in isolation, its overt expression damages the play’s texture. Giving the game away at the opening robs audiences of the pleasure of discovering the idea from Hellman’s subtext.

Isolation, as it turns out, bedevils almost all the performances. Ideally dressed by designer Mark Thompson in plain, dark colors, both Knightley and Moss are wholly convincing as dedicated, no-nonsense, slightly worn-down teachers at the school they started together. What’s less successful is their portrayal of a convincingly textured best-friend relationship.

Moss’ unadorned, plain-speaking Martha is the stronger of the two. She’s at her most vivid as she rages at Mary’s life-wrecking lie. But as the realization dawns upon her that Mary may inadvertently have revealed the truth about her own suppressed feelings, the energy of her pain remains within her body rather than radiating outward. Her self-realization should make emotional sense of something already half-expressed, but here it feels like a new plot twist because so little has been seen happening between the two of them.

Knightley is touching as Karen, who is upset to realize she has misjudged both Martha’s feelings and her understanding of her fiance, Joe (an oddly swaggering Tobias Menzies, sporting an American accent that seems to come from a gangster movie rather than the mouth of a well-educated, well-meaning local doctor).

Unlike film acting that mostly relies on reacting — intensity revealed in closeup with edits supplying energy and force — stage acting requires actors to charge up the space around and between them. Although closeups would undoubtedly reveal Knightley feeling everything, she isn’t able to project those feelings theatrically.

She is, surprisingly, not helped by the direction. “You’ll be all right?” asks Burstyn’s Amelia kindly, a line that makes no sense given that, at this point, Rickson has Knightley down on all fours at her physically lowest ebb.

That mismatch is indicative of a director surprisingly off-stride. With the actors all isolated in various degrees of extremity — Carol Kane madly flaky, several of the schoolgirls zealously over-characterized — the gears don’t mesh. That in turn exposes the plotting as increasingly contrived despite a grounded physical production with Mark Thompson’s evocative, clapboard-house designs lit with haunting pale intensity by Neil Austin.

Headline casting has ensured a near total instant SRO run (despite high ticket prices) and a likely Gotham engagement. But for this fitful vehicle to achieve dramatic momentum, pages need to be taken from Burstyn’s book. More calmly connected work like hers, and this fairly effective show could be truly affecting.